Investigations are being conducted into aspects of specialization of the primate and human retinochoroidal complex with emphasis on the pigmented epithelium. Mammalian (including human) pigmented epithelial choroidal cells are being cultured on various substrata with media containing various growth factors and hormones so that these cells may exhibit maximal proliferative capacity. Cell- and tissue-specific marker enzymes such as tyrosinase are being assayed to determine the extent to which the cells are as differentiated as their in vivo counterparts. The extracellular matrix material from cultured RPE and choroid is being analyzed biochemically and by means of light and electron microscopic immunocytochemistry and the results compared with those from normal and pathologic tissues.